network+ 6th edition chapter 05
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The presentations cover the objectives found in the opening of each chapter. All chapter objectives are listed in the beginning of each presentation. You may customize the presentations to fit your class needs. Some figures from the chapters are included. A complete set of images from the book can be found on the Instructor Resources Website. Course Technology - CENGAGE LearningTRANSCRIPT
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Network+ Guide to Networks6th Edition
Chapter 5 Topologies and Ethernet Standards
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Objectives
• Describe the basic and hybrid LAN topologies, and their uses, advantages, and disadvantages
• Describe the backbone structures that form the foundation for most networks
• Compare the different types of switching used in data transmission
• Explain how nodes on Ethernet networks share a communications channel
• Identify the characteristics of several Ethernet standards
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Simple Physical Topologies
• Physical topology– Physical network nodes layout– Depicts broad scope– Does not specify:
• Device types• Connectivity methods• Addressing schemes
• Fundamental shapes– Bus, ring, star– Hybrid
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Bus
• Bus topology– Single cable– Connects all network nodes– No intervening connectivity devices– One shared communication channel
• Physical medium– Coaxial cable
• Passive topology– Node listens for, accepts data– Uses broadcast to send
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Bus (cont’d.)
• Terminators– 50-ohm resistors– Stop signal at end of wire
• Signal bounce– Signal travels endlessly between two network ends
• One end grounded– Removes static electricity
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Figure 5-1 A terminated bus topology network
Network+ Guide to Networks, 6th Edition
Courtesy Course Technology/Cengage Learning
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Bus (cont’d.)
• Bus topology advantage– Relatively inexpensive
• Disadvantages– Does not scale well– Difficult to troubleshoot– Not very fault tolerant
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Ring
• Ring topology– Node connects to nearest two nodes– Circular network– Clockwise data transmission
• One direction (unidirectional) around ring– Active topology
• Workstation participates in data delivery• Data stops at destination
– Physical medium• Twisted pair or fiber-optic cabling
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Ring (cont’d.)
• Drawbacks– Malfunctioning workstation can disable network– Not very flexible or scalable
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Figure 5-2 A ring topology network
Courtesy Course Technology/Cengage Learning
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Star
• Star topology– Node connects through central device
• Router or switch
• Physical medium– Twisted pair or fiber-optic cabling
• Single cable connects only two devices• Advantage
– Fault tolerant– Flexible
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Star (cont’d.)
• Most popular fundamental layout– Modern Ethernet networks based on star topology
• 1024 addressable logical network nodes maximum
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Figure 5-3 A star topology network
Courtesy Course Technology/Cengage Learning
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Hybrid Topologies
• Pure bus, ring, star topologies– Rarely exist because too restrictive
• Hybrid topology– More likely– Complex combination of pure topologies– Several options
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Star-Wired Ring
• Star-wired ring topology– Star physical topology– Ring logical topology
• Benefit– Star fault tolerance
• Network use– Token Ring networks
• IEEE 802.5
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Star-Wired Ring (cont’d.)
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Figure 5-4 A star-wired ring topology network
Courtesy Course Technology/Cengage Learning
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Star-Wired Bus
• Star-wired bus topology– Workstation groups
• Star-connected devices• Networked via single bus
• Advantage– Cover longer distances– Easily interconnect, isolate different segments
• Drawback– Cabling, connectivity device expense
• Basis for modern Ethernet networks
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Star-Wired Bus (cont’d.)
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Figure 5-5 A star-wired bus topology networkCourtesy Course Technology/Cengage Learning
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Logical Topologies
• Refers to way data transmitted between nodes– Rather than physical layout
• Does not necessarily match physical topology• Most common: bus and ring• Broadcast domain
– All nodes connected to single repeating device or switch
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Backbone Networks
• Cabling connecting hubs, switches, routers• More throughput• Large organizations
– Fiber-optic backbone– Cat 5 or better for hubs, switches
• Enterprise-wide network backbones – Complex, difficult to plan
• Enterprise– Entire organization– Significant building block: backbone
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Serial Backbone
• Simplest backbone– Two or more devices– Connect using single medium in daisy-chain fashion
• Daisy-chain– Linked series of devices
• Benefit– Logical growth solution
• Modular additions– Low-cost LAN infrastructure expansion
• Easily attach switches
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Serial Backbone (cont’d.)
• Backbone components– Gateways, routers, switches
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Figure 5-6 A serial backbone
Courtesy Course Technology/Cengage Learning
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Serial Backbone (cont’d.)
• Serial connection of repeating devices– Limited distance spanned between each
• Standards – Define number of repeating devices allowed– Exceed standards
• Intermittent, unpredictable data transmission errors
• Not used in modern networks
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Distributed Backbone
• Connectivity devices– Connected to hierarchy of central connectivity devices
• Benefit– Simple expansion, limited capital outlay
• More complicated distributed backbone– Connects multiple LANs, LAN segments using routers
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Distributed Backbone (cont’d.)
• Additional benefits– Workgroup segregation– May include daisy-chain linked repeating devices
• Consider length
• Drawback– Potential for single failure points
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24Network+ Guide to Networks, 6th Edition
Figure 5-7 A simple distributed backboneCourtesy Course Technology/Cengage Learning
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Figure 5-8 A distributed backbone connecting multiple LANsCourtesy Course Technology/Cengage Learning
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Collapsed Backbone
• Uses router or switch– Single central connection point for multiple
subnetworks• Highest layer
– Single router or switch with multiprocessors• Central router failure risk• Routers may slow data transmission• Advantages
– Interconnect different subnetwork types– Central management
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27Network+ Guide to Networks, 6th Edition
Figure 5-9 A collapsed backbone
Courtesy Course Technology/Cengage Learning
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Parallel Backbone
• Most robust network backbone• More than one central router, switch
– Connects to each network segment• Requires duplicate connections between
connectivity devices• Advantage
– Redundant links– Increased performance– Better fault tolerance
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29Network+ Guide to Networks, 6th Edition
Figure 5-10 A parallel backbone
Courtesy Course Technology/Cengage Learning
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Switching
• Logical network topology component• Determines connection creation between nodes• Three methods
– Circuit switching– Packet switching– Multiprotocol label switching
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Circuit Switching
• Connection established between two network nodes– Before transmitting data
• Dedicated bandwidth• Data follows same initial path selected by switch• Monopolizes bandwidth while connected
– Resource wasted• Uses
– Live audio, videoconferencing– Traditional telephone calls
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Packet Switching
• Most popular• Breaks data into packets before transporting• Packets
– Travel any network path to destination– Find fastest circuit available at any instant– Need not follow each other– Need not arrive in sequence– Reassembled at destination
• Requires speedy connections for live audio, video transmission
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MPLS (Multiprotocol Label Switching)
• Introduced by IETF in 1999• Enables multiple types of Layer 3 protocols:
– To travel over any one of several Layer 2 protocols• Most often supports IP• Common use
– Layer 2 WAN protocols• Offers potentially faster transmission than packet- or
circuit-switched networks
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MPLS (cont’d.)
• Advantages– Use packet-switched technologies over traditionally
circuit switched networks– Create end-to-end paths– Addresses traditional packet switching limitations– Better QoS (quality of service)
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Figure 5-11 MPLS shim within a frameCourtesy Course Technology/Cengage Learning
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Ethernet
• Most popular networking technology used on modern LANs
• Benefits– Flexible– Can run on various network media– Excellent throughput– Reasonable cost
• All variations– Share common access method
• CSMA/CD
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CSMA/CD (Carrier Sense Multiple Access with Collision Detection)
• Network access method– Controls how nodes access communications channel– Necessary to share finite bandwidth
• Carrier sense– Ethernet NICs listen, wait until free channel detected
• Multiple access– Ethernet nodes simultaneously monitor traffic, access
media
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CSMA/CD (cont’d.)
• Collision– Two nodes simultaneously:
• Check channel, determine it is free, begin transmission
• Collision detection– Manner nodes respond to collision– Requires collision detection routine
• Enacted if node detects collision– Jamming
• NIC issues 32-bit sequence• Indicates previous message faulty
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CSMA/CD (cont’d.)
• Heavily trafficked network segments– Collisions common
• Segment growth– Performance suffers– “Critical mass” number dependencies
• Data type and volume regularly transmitted
• Collisions corrupt data, truncate data frames– Network must detect and compensate
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39Network+ Guide to Networks, 6th Edition
Figure 5-12 CSMA/CD process
Courtesy Course Technology/Cengage Learning
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CSMA/CD (cont’d.)
• Collision domain– Portion of network where collisions occur
• Ethernet network design– Repeaters repeat collisions
• Result in larger collision domain– Switches and routers
• Separate collision domains
• Collision domains differ from broadcast domains
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41Network+ Guide to Networks, 6th Edition
Figure 5-13 Broadcast domains and collision domains
Courtesy Course Technology/Cengage Learning
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CSMA/CD (cont’d.)
• Ethernet cabling distance limitations– Effected by collision domains
• Data propagation delay– Data travel time too long
• Cannot identify collisions accurately• 100 or 1000 Mbps networks
– Three segment maximum connected with two repeating devices
• 10 Mbps buses– Five segment maximum connected with four
repeating devices
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Ethernet Standards for Copper Cable
• IEEE Physical layer standards– Specify how signals transmit to media– Differ significantly in signal encoding
• Affect maximum throughput, segment length, wiring requirements
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Ethernet Standards for Copper Cable (cont’d.)
• 10Base-T– 10 represents maximum throughput: 10 Mbps– Base indicates baseband transmission– T stands for twisted pair– Two pairs of wires: transmit and receive
• Full-duplex transmission– Follows 5-4-3 rule of networking
• Five network segments• Four repeating devices• Three populated segments maximum
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45Network+ Guide to Networks, 6th Edition
Figure 5-14 A 10Base-T network
Courtesy Course Technology/Cengage Learning
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Ethernet Standards for Copper Cable (cont’d.)
• 100Base-T (Fast Ethernet)– IEEE 802.3u standard– Similarities with 10Base-T
• Baseband transmission, star topology, RJ-45 connectors
– Supports three network segments maximum • Connected with two repeating devices• 100 meter segment length limit between nodes
– 100Base-TX• 100-Mbps throughput over twisted pair• Full-duplex transmission: doubles effective bandwidth
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47Network+ Guide to Networks, 6th Edition
Figure 5-15 A 10Base-T network
Courtesy Course Technology/Cengage Learning
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Ethernet Standards for Copper Cable (cont’d.)
• 1000Base-T (Gigabit Ethernet)– IEEE 802.3ab standard– 1000 represents 1000 Mbps– Base indicates baseband transmission– T indicates twisted pair wiring– Four pairs of wires in Cat 5 or higher cable
• Transmit and receive signals– Data encoding scheme: different from 100Base-T– Standards can be combined– Maximum segment length: 100 meters, one repeater
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Ethernet Standards for Copper Cable (cont’d.)
• 10GBase-T– IEEE 802.3an– Pushing limits of twisted pair
• Requires Cat 6, 6a, or 7 cabling• Maximum segment length: 100 meters
– Benefits• Very fast data transmission• Cheaper than fiber-optic
– Uses• Connect network devices• Connect servers, workstations to LAN
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Ethernet Standards for Fiber-Optic Cable
• 100Base-FX (Fast Ethernet)– 100-Mbps throughput, baseband, fiber-optic cabling
• Multimode fiber containing at least two strands– Half-duplex mode
• One strand receives; one strand transmits• 412 meters segment length
– Full duplex-mode• Both strands send and receive• 2000 meters segment length
– One repeater maximum– IEEE 802.3u standard
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Ethernet Standards for Fiber-Optic Cable (cont’d.)
• 1000Base-LX (1-Gigabit Ethernet)– IEEE 802.3z standard– 1000: 1000-Mbps throughput– Base: baseband transmission– LX: reliance on 1300 nanometers wavelengths– Longer reach than any other 1-gigabit technology– Single-mode fiber: 5000 meters maximum segment– Multimode fiber: 550 meters maximum segment– One repeater between segments– Excellent choice for long backbones
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Ethernet Standards for Fiber-Optic Cable (cont’d.)
• 1000Base-SX (1-Gigabit Ethernet)– Differences from 1000Base-LX
• Multimode fiber-optic cable (installation less expensive)• Uses short wavelengths (850 nanometers)
– Maximum segment length dependencies• Fiber diameter, modal bandwidth used to transmit
signals
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Ethernet Standards for Fiber-Optic Cable (cont’d.)
• 1000Base-SX (cont’d.)– Modal bandwidth measurement
• Highest frequency of multimode fiber signal (over specific distance)
• MHz-km• Higher modal bandwidth, multimode fiber caries signal
reliably longer– 50 micron fibers: 550 meter maximum length– 62.5 micron fibers: 275 meter maximum length– One repeater between segments– Best suited for shorter network runs
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10-Gigabit Fiber-Optic Standards
• Extraordinary potential for fiber-optic cable– Pushing limits
• 802.3ae standard– Fiber-optic Ethernet networks– Transmitting data at 10 Gbps– Several variations– Common characteristics
• Star topology, allow one repeater, full-duplex mode– Differences
• Signal’s light wavelength; maximum allowable segment length
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10-Gigabit Fiber-Optic Standards (cont’d.)
• 10GBase-SR and 10GBase-SW– 10G: 10 Gbps– Base: baseband transmission– S: short reach– Physical layer encoding
• R works with LAN fiber connections• W works with SONET fiber connections
– Multimode fiber: 850 nanometer signal transmission– Maximum segment length
• Depends on fiber diameter
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10-Gigabit Fiber-Optic Standards (cont’d.)
• 10GBase-LR and 10GBase-LW– 10G: 10 Gbps– Base: baseband transmission– L: long reach– Single-mode fiber: 1310 nanometer signal
transmission– Maximum segment length
• 10,000 meters– 10GBase-LR: WAN or MAN– 10GBase-LW: SONET WAN links
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10-Gigabit Fiber-Optic Standards (cont’d.)
• 10GBase-ER and 10GBase-EW– E: extended reach– Single-mode fiber
• Transmit signals with 1550 nanometer wavelengths– Longest fiber-optic segment reach
• 40,000 meters (25 miles)– 10GBase-EW
• Encoding for SONET– Best suited for WAN use
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Summary of Common Ethernet Standards
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Table 5-1 Common Ethernet standardsCourtesy Course Technology/Cengage Learning
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Courtesy Course Technology/Cengage LearningFigure 5-16 Multiple types of Ethernet on a WAN
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Ethernet Frames
• Four types– Ethernet_802.2 (Raw)– Ethernet_802.3 (Novell proprietary)– Ethernet_II (DIX)– Ethernet_SNAP
• Frame types differ slightly– Coding and decoding packets
• No relation to topology, cabling characteristics• Framing
– Independent of higher-level layers
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Using and Configuring Frames
• Ensure all devices use same, correct frame type– Node communication
• Ethernet_II used today• Frame type configuration
– Specified using NIC configuration software– NIC autodetect
• Importance– Know frame type for troubleshooting
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Frame Fields
• Common fields– 7-byte preamble, 1-byte start-of-frame delimiter– SFD (start-of-frame delimiter) identifies where data
field begins– 14-byte header– 4-byte FCS (frame check sequence)– Frame size range: 64 to 1518 total bytes
• Larger frame sizes result in faster throughput• Improve network performance
– Properly manage frames
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Ethernet_II (DIX)
• Developed by DEC, Intel, Xerox (abbreviated DIX)– Before IEEE
• Contains 2-byte type field– Identifies the Network layer protocol
• Most commonly used on contemporary Ethernet networks
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Figure 5-17 Ethernet II (DIX) frame
Courtesy Course Technology/Cengage Learning
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PoE (Power over Ethernet)
• IEEE 802.3af standard– Supplying electrical power over Ethernet connections
• Two device types– PSE (power sourcing equipment)– PDs (powered devices)
• Requires Cat 5 or better copper cable• Connectivity devices must support PoE• Compatible with current 802.3 installations
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PoE (cont’d.)
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Figure 5-18 PoE capable switch Figure 5-19 PoE adaptersCourtesy D-Link North America Courtesy D-Link North America
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Summary
• Physical topology describes basic network physical layout– Examples: bus, ring, star, hybrid
• Logical topology describes signal transmission• Network backbones
– Serial, distributed, collapsed, parallel• Switching
– Manages packet filtering, forwarding• Ethernet
– Cabling specifications, data frames, PoE
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